Problem: What do the following two equations represent? $-5x+5y = -2$ $-20x-20y = 2$
Putting the first equation in $y = mx + b$ form gives: $-5x+5y = -2$ $5y = 5x-2$ $y = 1x - \dfrac{2}{5}$ Putting the second equation in $y = mx + b$ form gives: $-20x-20y = 2$ $-20y = 20x+2$ $y = -1x - \dfrac{1}{10}$ The slopes are negative inverses of each other, so the lines are perpendicular.